1. Technical Field
The present invention relates to an optical disk apparatus which records and reproduces information on/from an optical disk such as a CD (compact disk) or a DVD (digital versatile disk), and an optical pickup device included in the optical disk apparatus.
2. Background Art
An optical disk apparatus which is generally used to record or reproduce information on/from an optical disk such as a CD or a DVD is shown in FIG. 14. In FIG. 14, an optical disk apparatus 1 has a housing 2 and a tray 3 which is held by the housing 2 such that the tray 3 can go in and out of the housing 2. The housing 2 has a pouched shape obtained by combining metal housing portions 2a and 2b, and the housing 2 is designed such that the tray 3 is inserted or removed in/from an opening of the housing 2. An optical pickup device 4 is attached to the tray 3 from a rear surface side of the tray 3. Rails 3a are slidably arranged on both side portions of the tray 3. The rails 3a are held by rail holding portions 3b integrally arranged on the tray 3.
The optical pickup device 4 has at least a spindle motor 5 which rotationally drives the optical disk, a metal cover 6 having an opening 6a extending from the spindle motor 5 to the outer circumference, and a carriage 7 partially exposed from the opening 6a. The carriage 7 is movably held by a plurality of guide shafts arranged on the optical pickup device 4. Furthermore, the carriage 7 can be moved by a feed motor (not shown) such that the carriage 7 approaches or leaves the spindle motor 5. Reference numeral 8 denotes a bezel arranged in front of the tray 3. The bezel 8 is designed to be large enough to fit the opening of the housing 2.
In the carriage 7, a light source such as a high-output laser diode, various optical members, an objective lens which forms an optical spot on an optical disk, and the like are mounted. When performing information recording on the optical disk, the high-output light source, an IC which drives the light source, and the like are necessary. As a result, lots of heat is generated by the light source and the IC and influences recording/reproducing characteristics.
In an optical pickup device for the CD or the DVD, in general, a light-receiving/emitting unit obtained by integrally arranging a light source portion such as a semiconductor laser and a light-receiving portion such as a photodetector is used. Since a quantity of heat generated by the light source portion in the light-receiving/emitting unit is large, heat must be removed from the light-receiving/emitting unit. On the other hand, since the light-receiving/emitting unit is molded with a resin material, it cannot be said that the light-receiving/emitting unit itself has a good heat radiation property. Therefore, heat radiation from the light-receiving/emitting unit must be considered.
Since a light-receiving/emitting unit included in an optical disk apparatus for CD is supported and fixed to a metal base configuring the carriage, heat generated by the light-receiving/emitting unit for CD can be directly conducted to the base (for example, see Japanese Unexamined Patent Publication No. 10-83551). Therefore, the heat radiation property of the CD light-receiving/emitting unit is relatively preferable.
On the other hand, since information is recorded on the DVD at a density higher than that of the CD, in an optical pickup device for DVD, slide adjustment and tilt adjustment must be performed in the light-receiving/emitting unit. In this case, the slide adjustment is adjustment to adjust an optical axis of an optical system having a collimating lens, an objective lens and the like. In this adjustment, on a plane (X-Y plane) parallel to a radiation reference plane of a laser beam in the DVD light-receiving/emitting unit, the DVD light-receiving/emitting unit is moved to correct the optical axis. The tilt adjustment is adjustment to correct an inclination of a light-emitting angle of the laser beam from a laser beam source.
Therefore, in the optical pickup device for DVD, the light-receiving/emitting unit must be able to be moved with respect to the base for the adjustment. For this reason, the light-receiving/emitting unit cannot be directly supported and fixed to the metal base configuring the carriage. Therefore, heat radiation from the DVD light-receiving/emitting unit poses a problem. For this reason, a plurality of approaches to solve the problem are made. Upon completion of the adjustment, the light-receiving/emitting unit is fixed to the base.
For example, in Japanese Unexamined Patent Publication No. 2005-196860, a configuration as shown in FIGS. 15 to 17 is disclosed. In this case, FIG. 16 is a diagram of an optical pickup when viewed from the lower surface side, and FIG. 17 is a diagram of the optical pickup when viewed from the upper surface side in a state that the lower surface and the upper surface of the optical pickup shown in FIG. 16 are upside-down. FIG. 15 is a perspective view of the optical pickup device 4 on which the carriage 7 is mounted in a state shown in FIG. 17. In the configuration in FIGS. 16 and 17, reference numeral 11 denotes a metal base, reference numeral 13 denotes a CD light-receiving/emitting unit, reference numeral 14 denotes a DVD light-receiving/emitting unit, reference numeral 15 denotes a tilt adjusting member, reference numeral 16 denotes a slide adjusting member, and reference numeral 21 denotes a heat radiation fin.
In the configuration shown in FIGS. 16 and 17, a first heat radiating sheet 17 and a heat radiating base 18 are sequentially attached to a side opposing the light-emitting surface of the DVD light-receiving/emitting unit 14 in the order of the sheet 17 and the base 18 from the DVD light-receiving/emitting unit 14 side. The first heat radiating sheet 17 and the heat radiating base 18 are pressed against the DVD light-receiving/emitting unit 14 by a press spring 19 and supported. Therefore, the first heat radiating sheet 17 is brought into contact with a surface opposing the light-emitting surface of the DVD light-receiving/emitting unit 14. In this manner, the press spring 19 is used to bring the first heat radiating sheet 17 into contact with the DVD light-receiving/emitting unit 14 to provide heat radiation and to make it possible to perform the slide adjustment and the tilt adjustment for the DVD light-receiving/emitting unit 14.
Furthermore, a second heat radiating sheet 20 is attached to cover the lower surfaces of the DVD light-receiving/emitting unit 14 and the tilt adjusting member 15. The lower surface mentioned here corresponds to an upper surface when viewed in FIG. 16. The second heat radiating sheet 20 is to efficiently conduct heat generated by the DVD laser unit 14 to the base 11 having a large heat capacity through the tilt adjusting member 15, and the second heat radiating sheet 20 is formed by a material such as graphite which is excellent in heat radiation property. In order to make it possible to perform slide adjustment and tilt adjustment for the DVD light-receiving/emitting unit 14, the second heat radiating sheet 20 is not in direct contact with the DVD light-receiving/emitting unit 14.
Even in the conventional configuration shown in FIGS. 15 to 17, the DVD light-receiving/emitting unit provides heat radiation which is sufficient to operate the optical pickup device including the slide adjusting member and the tilt adjusting member in the DVD light-receiving/emitting unit.
However, as described above, the first heat radiating sheet 17 is just pressed by the press spring 19 to be in contact with the DVD light-receiving/emitting unit 14 to secure the heat radiation capability. The second heat radiating sheet 20 is merely attached to cover the lower surfaces of the DVD light-receiving/emitting unit 14 and the tilt adjusting member 15. At this time, a medium such as grease to improve heat conductivity from the DVD light-receiving/emitting unit 14 to the tilt adjusting member 15 may be provided between the heat radiating sheet 20 and the lower surfaces of the DVD light-receiving/emitting unit 14 and the tilt adjusting member 15. However, it is not said that the medium has sufficient heat conductivity.
Therefore, a margin to further improve the heat radiation property of the DVD light-receiving/emitting unit is still present.